Four years later, we still have ten big questions

Reports on the FDNY response to 9-11 generally agree that, as the FDNY-commissioned McKinsey study put it, "Chief officers considered a limited, localized collapse of the towers possible, but did not think that
they would collapse entirely." For some of the fire officers, that confidence might have been based on a misconception about how the towers were built: The FDNY chief of safety says in his oral history that he thought the towers were made of block construction, with a solid concrete core, so that fire crews would have at least three hours to work. In fact, the cores of the towers were sheetrock over steel. And the citywide safety chief in charge that day didn't know a plane had hit the north tower.

Evidently, fears about collapse evolved as the disaster wore on. Peter Ganci, the highest ranking chief and one of the 343 fire personnel who died, reportedly told the commander in the north-tower lobby at 9:45 a.m. that he might want to consider an evacuationï¿½almost 45 minutes before that building collapsed. Assistant Chief Joseph Callan, the citywide tour commander that day, told investigators: "Approximately 40 minutes after I arrived in the lobby I made a decision that the building was no longer safe and that was based on the conditions in the lobbyï¿½large pieces of plaster falling, all the 20-foot-high glass panels on the exterior of the lobby were breaking, there was obvious movement of the building, and that was the reason on the handy talky I gave the order for all fire department units to leave the north tower. Approximately ten minutes after that we had collapse of the south tower." Fire chiefs also receivedï¿½just moments before the south tower fellï¿½a report that someone from the city's Office of Emergency Management thought the towers weren't structurally sound. The source of that report is unknown.

photo: Joe Zeff

Details

A constant refrain in rehashes of 9-11 is that the cooperation between police and fire services that day was poor. The OEM was unable to bridge the gap because it was busy evacuating its own emergency center in 7 WTC. "The loss of the OEM operations center," NIST found, "created difficulties related to the coordination of emergency responder operations and resources." Because the World Trade Center had been a terrorist target in 1993, Giuliani was criticized in 1998 for his decision to locate the emergency center there. Yet when Giuliani and Jerry Hauer (who was OEM director when the 7 WTC site was picked) appeared before the 9-11 Commission, no one asked them about the bunker. Nor did commissioners ask Giuliani specifically why firefighters were using the same radios on 9-11 that had worked so poorly in the '93 bombing. Part of the reason was the city had broken contracting rules when it purchased new radios earlier in 2001, and those radios had to be withdrawn because of technical problems.

6. Why did 7 WTC fall?

Seven World Trade Centerï¿½where, besides OEM, the CIA, Salomon Smith Barney, and other entities had officesï¿½was the last building to collapse on 9-11. It was also probably the first steel skyscraper anywhere to collapse solely because of fire. We still don't know why. While NIST has completed its twin towers reports, it has delayed its 7 WTC report twice; it's currently not expected until next spring.

Several 7 WTC tenants, including OEM and the Secret Service, had tanks filled with diesel fuel to power emergency generators. If that fuel leaked and burned, it may have heated the building's steel supports to the point of failure, but according to FEMA's report on the collapse this "best hypothesis has only a low probability of occurrence."

9/11 Aftermathphoto: Charles Petersheim

7. How did the twin towers fall?

Many FDNY personnel who saw the south tower collapse reported explosions at the lower levels as the top began collapsing. These reports, as well as "squibs" of smoke seen on video of the collapses, have led to theories that the towers were brought down in controlled explosions. NIST dismisses these notions, claiming that the puffs of smoke were the result of air being forced down by the top of the tower collapsing.

NIST said the towers fell because the planes shook fireproofing loose from the steel superstructure, and the fire heated the floor-supporting trusses so much that they pulled in on support columns that were already holding more than their regular load. But NIST's computer simulation stops at the point the collapse begins, and does not document exactly how the rest of the buildings crumbled in 10 seconds. The reason for this omission could be the sheer complexity of the computationsï¿½even NIST's simplified model took weeks to run on a computer.

Conspiracy theorists aren't the only ones who dispute NIST's version: Some fire scientists also take issue with the institute's methods and conclusions. And the point isn't just historical. The lessons learned from the WTC collapse will inform decisions about the safety of other modern office towers.

8. How dangerous wasï¿½and isï¿½the air at ground zero?

A few days after the towers fell, the Environmental Protection Agency announced that tests of air and water near the WTC site "indicate that these vital resources are safe." The only problem was, as the EPA's inspector general reported later, the agency "did not have sufficient data and analyses to make such a blanket statement." What's more, the inspector general said, "the White House Council on Environmental Quality influenced, through the collaboration process, the information that EPA communicated to the public."